1. Field of the Invention
The present Invention generally relates to tools or machines in which accurate, quick and easy adjustment of the relative positions of two components is desirable. More particularly, but not exclusively, the present invention relates to an apparatus for eliminating play in the threaded interconnection of mechanical elements of a power tool or machine which is most evident upon reversal of movement, otherwise known as backlash.
2. Discussion
Various power tools are used in woodworking and metal forming to efficiently and accurately shape workpieces to desired dimensions and surface qualities. Such tools often include a workpiece forming element such as a bit, cutting blade, or the like, which is adjustable relative to the workpiece. For example, the workpiece forming element, in many instances, is adjustable relative to a base plate or platen upon which the workpiece is supported. Many applications require quick and accurate adjustment of the workpiece forming element to obtain desired results.
A wood planing machine is one example of such a tool in which a workpiece forming element is adjustable relative to a workpiece. A conventional planing machine is used for the surface planing of boards and typically includes one or more rotatably mounted cutting blades attached to a vertically movable carriage assembly. In a typical wood surface planer, a selectively adjustable workpiece opening is defined between a carriage assembly and a workpiece support surface or platen. The one or more rotationally mounted cutting blades by the carriage assembly so as to be exposed adjacent to the workpiece opening. The carriage assembly is movably mounted to a plurality of support columns for movement with respect to the workpiece support surface, thereby permitting adjustment of the vertical dimension of the workpiece opening for selectively determining the amount of material to be removed from the workpiece.
Multiple passes of the workpiece through the workpiece opening are often necessary to obtain the desired thickness and surface quality. Through adjustment of the carriage assembly relative to the support surface, the amount of material removed during a single pass can be varied. Such adjustment is typically accomplished through selective rotation of a drive rod threadably engaged with the carriage assembly. As with other woodworking and metal forming operations, it is highly desirable that a planing machine accomplish workpiece preparation with precise tolerances, high surface quality, and a significant degree of reproducible results.
While many commercially successful tools are available which include an adjustable workpiece forming element that is linearly advanced by a rotatable drive rod, all are subject to improvement. Most specifically, the necessary thread clearances between the component carrying the workpiece forming element and the rotatable drive rod creates play In the interconnection therebetween which is most evident upon reversal of movement of the drive rod. As a result, actual and perceived quality of the forming operation are adversely affected since initial reversing of rotation of the drive rod functions only to take up thread clearances and does not correspondingly result in translation of the workpiece forming element